Piezoelectric igniters which are manually actuatable generally comprise a spring-loaded hammer and an anvil juxtaposed with the hammer bearing against a piezoelectric crystal or other element, the output of which is applied across a pair of electrodes thereby generating a spark when the hammer, which is mechanically retained against the loading force, is instantaneously released.
Such piezoelectric igniters can be used in cigarette lighters to ignite a fuel such as butane which can be released by the mechanical movement that also ultimately triggers the formation of the spark.
The igniter with which the present invention is concerned generally comprises a female housing or sleeve which is closed at one end and receives the male member of the device, namely a casing whose outer configuration is cylindrical to mate with a cylindrical bore of the female member.
The casing, in succession from its external end toward the female member, is provided with a metallic anvil which may form one electrode in contact with the piezoelectric element, the piezoelectric element or crystal and a metallic abutment engaging the piezoelectric crystal from the opposite side.
Braced against the bottom of the female body within the latter and sealed against the inner end of the casing is a restoring spring which biases the female part and the casing away from one another against the manual actuation force.
Coaxial with this helical spring and forming an inner helical spring is another coil spring seated against the closed bottom of the female part of the housing and braced against a hammer which can be driven against the abutment in the manner previously described.
The hammer is formed with a pair of lateral projections defined by a pin extending through a transverse bore in the hammer to form diametrically opposite lugs each of which is received in a window formed in an adjacent portion of the wall of the female body and a longitudinal guide groove or slot formed in the casing. The inner end of the casing has a notch at the respective slot constituting a catch in which the respective lug is anchored, the lug being pushed into the catch by the action of a ramp provided in the transversal boundary or border of the window and against which the lug is applied by the action of the aforementioned springs.
From the notch the lug can be displaced by the action of another ramp inclined in the same sense but with inverse effect when the casing is pushed into the female part or the female part is pushed into casing by the manual action described. As the hammer is rotated to shift it out of the notch, the lugs are brought into line with the aforementioned slots and the drive spring, i.e. the inner one of the two springs, thus drives the hammer against the abutment to fire the spark. The actuating movement simultaneously compresses the spring so that the firing force applying the hammer against the piezoelectric element is enhanced.
In practice the transverse section of the cylindrical bore in the remale member and the external perimeter of the casing are circular which requires that the lugs be introduced after positioning of the hammer in the casing and in the female body and the application of the spring pressure.
This has, in the past, meant that the lugs were formed by a pin which was transversely inserted into a bore formed radially in the hammer.
This restriction of the hammer not only increases the cost of the device but also creates mounting and assembly problems which have not been satisfactorily resolved heretofore.